FUNGICIDES AND BACTERICIDES

Question 1

Fungicides

Eradicants vs. Protectants

Answer 1

Most fungicides are surface protectants that must be applied before fungal spores have germinated. The presence of protectants prevents germination of spores or kills them once having entered. If infection occurs, protectants cannot prevent the disease. (Susceptible to weathering).

Eradicants directly affect pathogens after they have invaded plant tissue by killing the fungus inside the host or by suppressing sporulation of the fungus. Many are systemics and can control established infections to a limited extent. (Susceptible to resistance). Beginning to replace protectants.

Question 2

Pesticides for Disease Control

Answer 2

Bactericides
Fungicides
Fumigants

Question 3

Bactericides

Answer 3

Consist primarily of -copper compounds,

• certain antibiotics, and
• natural bactericides

Question 4

Natural Bactericides (Biologicals)

Answer 4

• Agrobacterum radiobacter, strain K84-for the control of crown gall in fruit trees
• Pseudomonas fluorescens-strain 506-for the control of fire blight in pears.
• Bacillus subtilis against a range of fungal pests including those causing powdery mildew and Alternaria leaf blights.

Question 5

Antibiotics

Answer 5

Substances produced by microorganisms that are toxic and inhibit the proliferation of other microorganisms.
Examples include streptomycin and tetracycline and have been formulated into bactericides. Absorbed by the plant, these are only active on certain crops.